The present invention relates to molds used in injection molding machines. More particularly, the present invention relates to a latching device for use with an injection mold that includes removable inserts, to facilitate removal or changing of the mold inserts.
An injection molding machine operates so rapidly that it can quickly finish a run of a particular molded part in a comparatively short period of time. In view of the substantial cost of the machine, it should not be allowed to sit idle. When changing the set-up of the molding machine from production of one part to another, the article-forming mold in the machine has to be removed and a new mold inserted so that the machine can begin to operate and produce the new molded part. The time taken in changing the mold must be minimized so the machine can begin productive use as soon as possible. It currently takes from one to several hours to complete a complete mold change. The time lost in the mold change process has a marked effect on the profitability of a molding business.
Master Unit Die Products, Inc. (xe2x80x9cMUDxe2x80x9d) significantly reduced the time required for mold changes with its invention of a xe2x80x9cQuick Change System for Mold Basesxe2x80x9d as described in U.S. Pat. No. 5,350,289. The MUD quick change system is used with molds having adapter frames that are attached to the platens of the injection molding machine. The adapter frames are readily transferable from machine to machine using the existing mounting hole patterns on the platens of the machines. The molds are typically supported on ear plates that are adapted to support many different size molds. The ear plates are also readily transferable from adapter frame to adapter frame. The adapter frames have a U-shaped guide and support channel for receiving the ear plates on the mold base. T-shaped guide rollers are mounted in line with the entrance to each side of the guide channel. The T-shape configuration for the guide rollers enables the edge of the ear plate to roll along the vertical portion of the xe2x80x9cTxe2x80x9d while the larger horizontal portion of the xe2x80x9cTxe2x80x9d captures the ear plate, keeping the ear plate in line with the guide channel on the adapter frame. The adapter frames are attached to the platen faces using the existing standard threaded hole pattern on the platen face. Clamps can be used for the initial installation of the adapter frame. The clamps are preferably removed after bolts or cap screws, or the like, are used to fasten the adapter plates to the face of the platen. When the ear plate is inserted into the adapter frame, all of the fasteners are covered, eliminating a potential source of damage during the operation of the machine. The MUD quick change system allows mold assemblies that are equipped with standard ear plates to be changed in a molding machine in ten minutes, or even less time.
However, when the MUD frame is used with a hot runner manifold system, the xe2x80x9cAxe2x80x9d side frame that accepts the xe2x80x9cAxe2x80x9d side insert is bolted to the hot runner system nozzle plate. If the MUD inserts need to be changed to a different set, the xe2x80x9cAxe2x80x9d side mounting screws have to be removed, and the xe2x80x9cAxe2x80x9d side has to be pulled away from the hot runner system, so that the nozzles are pulled out of the seal-off and gate well in the mold frame. This is necessary to obtain sufficient clearance so that the nozzles of the hot runner system do not interfere with removal of the inserts and installation of the replacement mold inserts. The removal of the xe2x80x9cAxe2x80x9d side mounting screws is time consuming and slows the process of changing the mold inserts significantly, somewhat negating the advantage of the MUD quick change concept.
Briefly stated, in accordance with one aspect of the present invention, a latching device is provided that uses a cam action to hold the xe2x80x9cAxe2x80x9d side plate against the hot runner system (nozzle plate) during operation, thus replacing the screws used in prior art mold constructions. Preferably, the latching device is provided on each side of the mold to hold most effectively the xe2x80x9cAxe2x80x9d side plate against the nozzle plate during the high pressure injection of plastic melt.
For purposes of a mold insert change, each latch is rotated to release the xe2x80x9cAxe2x80x9d side plate from the nozzle plate, and hold the xe2x80x9cAxe2x80x9d side plate against the xe2x80x9cBxe2x80x9d side of the mold. This enables the xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d portions of the mold assembly to be moved away from the nozzle plate, thereby avoiding interference between the hot runner nozzles and xe2x80x9cAxe2x80x9d side insert and enabling quick mold insert change.
The latching device of the present invention includes dowel pins in both the nozzle plate and xe2x80x9cBxe2x80x9d side plate. A pivoting latch arm is configured to engage one or the other of the pins, depending on the function to be performed. The latch arm pivots on a center hub with and offset to provide a cam-tightening effect when the hub is rotated by a latch lever. The latch is engaged with the dowel in the nozzle plate during operation. To perform a mold insert change: (i) the clamp mechanism of the molding machine is operated to close the mold, (ii) the center hub of the latching device is rotated using a lever to release the latching force between the xe2x80x9cAxe2x80x9d side and nozzle plate, (iii) the latch arm is rotated to engage the pin on the xe2x80x9cBxe2x80x9d side, (iv) the center hub is rotated by the latch lever to generate a latching force between the xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d sides, (v) a safety pin is inserted in the latch arm, (vi) the clamp mechanism of the molding machine is operated to open the mold, moving the xe2x80x9cBxe2x80x9d and xe2x80x9cAxe2x80x9d sides together to clear the hot runner nozzles, (vii) the mold inserts are removed, (viii) new mold inserts are installed, and (ix) sequence is reversed so that latch arm ends tightly engaged with the pin in the nozzle plate.
Accordingly, the latching device of the present invention provides for a time-saving means of releasing and connecting a mold assembly and a hot runner manifold system.